Control for heating systems



Oct. 2, 1934. D. J STEWART 1,975,130

I CONTROL FOR HEATING SYSTEMS Original Filed Sept. 5, 1931 INVENTOR To LINE v lzgmcan JSZewarz WWW: W

ATTORNEYS Patented 0a.. 2,' 1934 PATENT OFFICE CONTROL FOR HEATING SYSTEMS Duncan J. Stewart, Rockford, Ill., assignor to Howard D. Colman, Rockford, Ill.

Application September 5,

1931, Serial No. 561,493

Renewed October 16, 1933 2 Claims. (Cl. 236-38) This invention relates to thermostatically controlled heating systems and more particularly to a system in which a current ,of air induced by a power blower is passed wholly or in part through a heater and its temperature thereby increased to a value predetermined by a control thermostat. In such systems, the proportion of the air forced through the heater and therefore the temperatureof the discharged air is determined by a position of a regulating damper whose movements are governed by a thermostat.

The object of the present invention is to provide a novel automatic-control in a system of the above character by which the blower is maintained in operation only when needed.

In carrying out this invention, the damper which governs the proportion of the air current passed through the heater is moved through variable distances in opposite directions by a control motor, and the movement of the damper into and out of a position in which all of the air is by-passed around the heater is utilized to interrupt and resume the;operation of a motor driving said blower.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawing which is a schematic view of a heating system embodying the teatures of the present invention. In this exemplary system, heat is conveyed to the room to be heated by air forced upwardly through a casing 1 by a blower or fan 2 disposed within the casing and arranged to be driven by an electric motor 3. The blower draws air into the casing through a fresh air opening 4 and recirculating opening 5 and discharges a current of air upwardly toward a casing 6 containing a heating coil and cooperating with the rear casingwall to define a passageway '7 through which part or all of the air current may be by-passed around the heater.

The proportion of the incoming air passed through the heater is determined by the position of a valve member in the form of a damper, 8 pivoted at 9 to swing between a full-cooling. position against an abutment 10 in which the entire air current is byrpassed around the heater through the passage 7 and a full-heating posi-. tion against an abutment 11 in which all of the air is forced through the heater.

Through the medium of a crank 12, a link 13,

and a bell crank 14, a link 15 and a crank 16,

capable of moving the shaft variable distances in opposite directions between two positions corresponding to the limit positions of the damper. Herein the driving means is a reversible electric motor 18 comprising a stator 19 of the core type enclosed by a main winding 20 and defining two poles on opposite sides of a squirrel-cage rotor 21. Shifting of the magnetic field around the rotor to initiate and maintain rotation thereof, when the winding 20 is energized by alternating current, is produced by the well known action of shading rings 22 and 23 each enclosing one side portion of a motor pole and comprising in the present instance, a relatively large number of turns of wire.

, The coils of each pair 22 and 23 are connectedinseries relation and disposed on diametrically opposite sides of the rotor. From the well known action of such coils, it will be understood that when the coils 22 are rendered effectual by shortcircuiting the same, the magnetic flux threading the pole sections enclosed by these coils will lag behind the flux in the unshaded sections enclosed by the then ineffectual coils 23 with the result that the magnetic field will shift around the rotor in a counter-clockwise direction and produce rotation of the rotor in the same direction. In a similar way, a clockwise rotation is produced by short-circuiting the coils 23 while the coils 22 remain ineffectual. Owing to the poor single phase characteristics of .the motor above described, rotation will cease when the circuits for both pairs of shading coils are interrupted and the position of the damper will be maintained dueto the friction in the speed reduction gearing.

Selective Short-circuiting of the shading coils to determine the direction and extent of move-' ment ofthe damper 8 is efiected under the control of a thermostat 24. having two swicthes 25 and 26 with a common terminal connected by a conductor 27 to each pair of shading coils. The insulated terminals of these switches are spaced apart so that both switches may be open simultaneously when the proper temperature prevails. These terminals are connected respectively to the insulated ends of the coils 22 and 23 by conductors 28 and 29 respectively in which are interposed switches 30 and 31. The latter constitute limit switches which are opened by cams 32 on the shaft 17 when the damper reaches its limit positions against the stops 11 and 10 respectively.

.The winding 20 is constantly energized from the secondary of a transformer 20 whose primary lid the thermostat calls for heat, the switch as will be closed and the coils 22 short -circuited initiating rotation oi the motor in a direction to advance the damper toward the abutment i1 and allow more air to be passed through the heater 6. When the proper room temperature is attained, the switch 26 is opened and the control motor stopped. In a similar way, closure of the switch 25 when the room temperature rises above that for which the thermostat is set, starts the motor in a direction to move the damper toward the abutment lil thereby causing more air to be bypassed around the heater and the temperature of the mixed air thereby decreased. In this way the thermostat governs the extent as well as the initiation of motor operation.

. J-Vhen the room temperature exceeds that for which the thermostat is set for a sufiicient period of time to enable the damperto reach its fullcooling position against the stop 10, it is no longer necessary to maintain the blower in op-- this end, the circuit 33 for the blower motor 3 is controlled by a switch 34 normally opened by a spring 35 and adapted to be closed upon energization of a relay coil 36 whose armature is connected to the movable contact of the switch 34;. The terminals of the coil are connected to those of the low voltage power source 33 through the medium of conductors 37 and 38 in the latter of which is interposed a switch 39. The movable contact or the latter is on the follower of a cam atlast on the shaft 17 and shaped to allow the switch 39 to open as the damper reaches its fullcooling position against the stop 10. For all other positions of the damper 8, the cam 40 maintains the switch 39 closed and the relay 36 excited, thereby maintaining the blower motor switch 34 closed In this Way the operation of the blower motor 3 is interrupted upon the movement of the v damper 8 into full-cooling position and its oporation is resumed iediately upon movement of the damper away from such position.

I claim as my invention:

1. in a temperature control system, the combination of a blower for inducing the flow of a heated air current, a damper movable varying distances in opposite directions to control the amount of heat supplied to said air current, a rotary shaft connected to said damper for moving the same between full-heating and fidl-cooling positions, electric motor means for driving said shaft having two windings adapted to be energized selectively to determine the direction of movement of said shaft, a thermostat controlling said windings selectively and acting to determine the extent of movement of the shaft by said drivtill) ing means, a switch adapted when closed to start' said blower and when open to interrupt the blower operation, and means on said shaft acting to open said switch when the shaft moves to full cooling position and to maintain said switc closed in all other positions of the shaft.

2. An air conditioning system having,- in combination. a blower for inducing the circulation of a current of air, an electric motor for driving said blower, a regulating device movable varyingdistances in opposite directions and operating'to change the condition of said air current according to its position, electric motor means having two windings energizable selectively to cause movement of said device at a slow and. graduated rate in opposite directions toward and away from a predetermined limiting position, a sensitive control instrumentality responsive to changes in the condition of the air and arranged to control;

the energization of said windings and thereby govern the direction and extent of movement of said device, a switch governing the starting and stopping of said blower motor and arranged to respond to the movement of said device so as to;

be opened and closed substantially-coincident to 

